1. Field of the Invention
The present invention relates to a plasma display apparatus, and more particularly, to a plasma display apparatus for connecting a film-type front filter.
2. Description of the Related Art
Plasma display panel (hereinafter referred to as “PDP”) generally displays an image including character or graphic by exciting phosphor using ultraviolet rays with a wavelength of 147 nm, which is generated during a gas discharge of an inert mixture gas, such as He+Xe, Ne+Xe, He+Ne+Xe or the like. This PDP has easy slimness and large-sized characteristics, and provides a greatly improved picture quality thanks to the recent technology development. In particular, three-electrode alternating current (AC) surface discharge type PDP has advantages of a low voltage operation and a long life since wall charges stored on a surface in the course of discharge protect electrodes from sputtering generated by the discharge.
FIG. 1 is a view illustrating a discharge cell of a conventional three-electrode alternating current (AC) surface discharge type plasma display panel.
Referring to FIG. 1, a discharge cell of the three-electrode AC surface discharge type PDP includes a scan electrode (Y) and a sustain electrode (Z) formed on an upper substrate 10, and an address electrode (X) formed on a lower substrate 18. Each of the scan electrode (Y) and the sustain electrode (Z) includes transparent electrodes 12Y and 12Z and metal bus electrodes 13Y and 13Z having line widths narrower than line widths of the transparent electrodes 12Y and 12Z formed at one-sided edge regions of the transparent electrodes 12Y and 12Z.
The transparent electrodes 12Y and 12Z are generally formed of Indium-Tin-Oxide (Hereinafter, referred to as “ITO”) on the upper substrate 10. The metal bus electrodes 13Y and 13Z are generally formed of chrome (Cr) on the transparent electrodes 12Y and 12Z to function to reduce a voltage drop caused by the transparent electrodes 12Y and 12Z having high resistance. An upper dielectric layer 14 and a passivation film 16 are layered on the upper substrate 10 having the scan electrode (Y) and the sustain electrode (Z) formed in parallel with each other. The wall charge generated at the time of plasma discharge is stored in the upper dielectric layer 14. The passivation film 16 prevents the upper dielectric layer 14 from being damaged due to the sputtering generating at the time of the plasma discharge and also, enhances an emission efficiency of a secondary electron. Magnesium oxide. (MgO) is generally used as the passivation film 16. A lower dielectric layer 22 and a barrier 24 are formed on the lower substrate 18 having the address electrode (X), and a fluorescent layer 26 is coated on a surface of the lower dielectric layer 22 and the barrier 24. The address electrode (X) is formed in a direction of crossing with the scan electrode (Y) and the sustain electrode (Z). The barrier 24 is formed in parallel with the address electrode (X) to prevent the visible ray and the ultraviolet ray caused by the discharge from being leaked to an adjacent discharge cell. The fluorescent layer 26 is excited by the ultraviolet ray generated due to the plasma discharge to radiate any one visible ray of red, green or blue. The inert mixed gas for the discharge such as He+Xe, Ne+Xe, He+Ne+Xe and the like is injected into a discharge space of the discharge cell provided between the upper/lower substrates 10 and 18 and the barrier 24.
In the PDP, one frame is divided for time-division driving into several sub-fields having different light-emitting times so as to embody a gray level of the image. Each of the sub-fields is divided into a reset period for which an entire screen is initialized, an address period for which a scan line is selected and a specific cell is selected at the selected scan line, and a sustain period for which the gray level is embodied depending on the light-emitting times.
For example, in case that the image is expressed using a 256 gray level as in FIG. 2, a frame period (16.67 ms) corresponding to 1/60 second is divided into eight sub-fields (SF1 to SF8). Also, each of the eight sub-fields (SF1 to SF8) is again divided into a reset period, an address period and a sustain period. Herein, the reset and address periods of each sub-field are identical every sub-field, whileas the sustain period is increased in a ratio of 2n (n=0, 1, 2, 3, 4, 5, 6, 7) at each of the sub-fields.
In the above-driven PDP, a front filter for shielding an electromagnetic interference and also preventing an external light from being reflected is installed on a front surface of the upper substrate 10.
FIG. 3 is a schematic section view illustrating a portion of a conventional plasma display apparatus.
Referring to FIG. 3, the conventional plasma display apparatus includes a panel 32 where the upper substrate 10 and the lower substrate 18 are attached to each other with a gap therebetween, a front filter 30 installed at a front surface of the panel 32, a chassis base 36 for supporting the panel 32 and also mounting a printed circuit board thereon, a heat sink plate 34 attached to a front surface of the chassis base 36, a back cover 38 installed on a rear surface of the panel 32, and a front cabinet 45 for electrically connecting the back cover 38 and the front filter 30.
The front cabinet 45 includes a filter support portion 40 for electrically connecting the front filter 30 and the back cover 38, and a support member 42 for fixing and supporting the front filter 30 and the back cover 38. The filter support portion 40 supports the front filter 30 such that a rear surface of the front filter 30 is spaced away from the panel 32. Further, the filter support portion 40 electrically connects the EMI shield film included in the front filter 30 to the back cover 38 grounded to a ground voltage source to discharge an EMI signal from the EMI shield film. Also, the filter support portion 40 prevents the EMI from being laterally emitted.
The printed circuit board mounted on the chassis base 36 supplies a driving signal to electrodes (for example, a scan electrode, a sustain electrode and an address electrode) of the panel 32. For this, the printed circuit board includes various driving portions not shown. The panel 32 displays a certain image in response to the driving signal supplied from the printed circuit board. The heat sink plate 34 dissipates heat generated from the panel 32 and the printed circuit board. The back cover 38 protects the panel 32 from an external impact, and also shields an electromagnetic interference (Hereinafter, referred to as “EMI”) laterally emitted.
The front filter 30 shields the EMI and also, prevents an external light from being reflected. For this, the front filter 30 includes an antireflection coating 50, an EMI shield film 54 and a near infrared ray (Hereinafter, referred to as “NIR”) shield film 56. The front filter 30 additionally includes a glass and a color correction film 58. Herein, an adhesive layer is formed between respective films 50, 52, 54, 56 and 58 of the front filter 30 to adhere respective films 50, 52, 54, 56 and 58 to one another. Generally, a color correction pigment is added to the adhesive layer to form the color correction film 58. At this time, a structure of the front filter 30 can be a little varied depending on providers.
The antireflection coating 50 prevents incident light from being reflected to thereby enhance the contrast of the PDP. The antireflection coating 50 is formed on a front surface of the front filter 30, and may be further formed on a rear surface of the front filter 30. The optical characteristic film 52 lowers the brightness of red (R) and green (G) colors of the visible light applied from the panel 32, and enhances the brightness of blue (B) color of the visible light thereby improving the optical characteristics of the PDP.
The glass 54 protects the front filter 30 from external impact. The glass 54 supports the front filter 30 such that the glass 54 may protect the front filter 30 from external impact.
The EMI shield film 56 screens the EMI to prevent the EMI applied from the panel from being released to the external. The NIR shield film 58 screens the NIR irradiated from the panel 32 to prevent the NIR from being irradiated more than the standard to the external so that signal transfer apparatuses may normally transfer a signal by the NIR as a remote controller. The EMI shield film 56 and the NIR shield film 58 can be configured in one layer.
The front filter 30 is electrically connected to the back cover 38 through the filter supporter 40 as shown in FIG. 5. The filter supporter 40 is connected to an edge portion of the rear surface of the front filter 30. The filter supporter 40 is electrically connected to at least one of the EMI shield film 56 and the NIR shield film 58. Therefore, the filter supporter 40 connects the front filter 30 to the back cover 38 to thereby screen the EMI and/or the NIR.
The conventional front filter 30 is protected from external impacts by glass 54. Such front filter 30 is called a glass-type entire filter. If the glass 54 is inserted into the front filter 30, the front filter 30 becomes thicker, heavier and more expensive.
To solve the above-mentioned problems, the front filter without the glass had been suggested as shown in FIG. 6. The front filter is called film-type front filter.
The film-type front filter 60 includes an antireflection coating 62, an optical characteristic film 64, an EMI shield file 66 and an NIR shield film 68. Adherence layers are formed between films 62, 64, 66 and 68 of the film-type front filter 60 such that the films 62, 64, 66 and 68 are attached to adjacent ones. In general, the optical characteristic film 64 is formed by inserting a specific material into the adherence layers. The structure of film-type front filter 60 can be modified variously according to a user company. In FIG. 6, the adherence layer is not shown for the convenience for the description and the optical characteristic film is depicted as a specific layer.
The antireflection coating 62 is formed on a front surface of the film-type front filter 60 to prevent incident light from being reflected. The antireflection coating 62 may be further formed on a rear surface of the film-type front filter 60. The optical characteristic film 64 lowers the brightness of red (R) and green (G) colors of the visible light applied from the panel 32, and enhances the brightness of blue (B) color of the visible light thereby improving the optical characteristics of the PDP.
The EMI shield film 66 screens the EMI to prevent the EMI applied from the panel from being released to the external. The NIR shield film 68 screens the NIR irradiated from the panel 32 to prevent the NIR from being irradiated more than the standard to the external so that signals may be normally transferred from a remote controller to a panel 32. The EMI shield film 66 and the NIR shield film 68 can be configured in one layer.
The film-type front filter 60 is thinner, lighter and cheaper than the front filter 30 with the glass 54.
However, a plasma display apparatus with a film-type front filter and a method for manufacturing the same have not been suggested so that the film-type front filter is not widely used.